Portable electronic calculator power supply

ABSTRACT

A power supply for use in a portable, hand-held calculator which comprises positive, negative, and reference terminals, and a plurality of batteries connected electrically in series between the positive and reference terminals. A means for generating a negative voltage is coupled to the batteries and between the negative and reference terminals, the generating means including an oscillator circuit having an input circuit coupled to the positive terminal, an output circuit, a rectifier circuit, and means coupling the rectifier circuit to the output circuit.

United States Patent 1 1 3,743,920 Ubillos 1 July 3, 1973 t [54]PORTABLE ELECTRONIC CALCULATOR 3,267,288 4/1966 Maiden et a1 307/48 X3,384,803 5/1968 Hardin et al 307/1 1 X POWER SUPPLY 3,417,311 12/1968Logan 321/2 [75] Inventor: Peter Ubillos, Franklin, Mass. [73] Assignee:Bowmar/Ali, 1nc., Acton, Mass. Primary ShOOP,

Attorney- Harold B. Hood. Ronald D. Welch et al.

[22] Filed: July 17, 1972 Appl. No.: 272,41 1

[5 7 ABSTRACT 7 Claims, 1 Drawing Figure PORTABLE ELECTRONIC CALCULATORPOWER SUPPLY BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention relates to direct current power supplies for small,portable electronic equipment such as a hand-held calculator, and inparticular to such a power supply which utilizes batteries forgenerating a primary, positive voltage source and an oscillator circuitcoupled to the batteries for generating a lower power negative voltagesource.

2. Description of the Prior Art Power supplies used to energize portableelectronic equipment are well known, such power supplies typicallyutilizing batteries as their primary source of energy. In one type ofpower supply well known in the prior art, the batteries are used toenergize the circuit directly, with proper voltages for the circuitbeing obtained by proper selection of the number of cells used. Positiveand negative polarity sources are provided by using two sets ofbatteries. In another typical type of prior art power supply whereinhigher voltages are required, it has been a common practice to usebatteries as a primary source of energy and to couple thereto some formof a chopper or oscillator circuit and a transformer to attain therequired voltages. This latter type of power supply has also been widelyadopted for -use in circuits which require both positive and negativevoltage sources.

When both positive and negative polarity sources are required foroperating a circuit, it is frequently the case that the positive andnegative supplies are required to meet substantially different powerrequirements. Correspondingly, portable power supplies of the typeutiliz- Y SUMMARY OF THE INVENTION Broadly, the invention is a powersupply for use in a portable, hand-held calculator. The power supplycomprises positive, negative, and reference terminals, and a pluralityof batteries connected electrically in series between the positive andreference terminals. A means is provided for generating a negativevoltage, the means being coupled to the batteries and between thenegative and reference terminals. The generating means includes anoscillator circuit having an input circuit coupled to the positiveterminal, an output circuit, a rectifier circuit, and means couplingtherectifier circuit to the output circuit.

This novel power supply circuit utilizes batteries to provide a firstsource of first polarity and the chopper circuit to provide a secondsource of opposite polarity. The battery source has a substantiallyhigher power capacity than the chopper" source. By using batteriesdirectly for the higher power source, circuit losses are minimized.Similarly, by using an oscillator circuit for the lower power source,minimum power is consumed therein, and no need for different types ofbatteries, and no excessive power capacity results.

In one specific embodiment of the invention, there is also provided adisengageable charging module which includes means for charging thebatteries of the power supply and means for supplying a positivepolarity supply to operate an external circuit while the batteries arebeing charged. 1

It is therefore an object of the invention to provide an improved powersupply for use in a portable, handheld calculator circuit.

It is another object of the invention to provide such a power supplywhich provides positive and negative polarity sources.

It is still another object of the invention to provide such a powersupply which provides positive and negative power sources havingdifferent load capacities with maximum efficiency. I

It is another object of the invention to provide such a power supplywherein the higher capacity source is provided directly by a pluralityof batteries and a lower capacity source is provided by an oscillatorcircuit operated from the higher source batteries.

It is still another object of the invention to provide such a powersupply which includes a detachable circuit for selectively charging thebatteries thereof.

It is yet another object of the invention to provide such a power supplywhich includes a charging module which also provides an alternate powersupply for oper-. ating a circuit when the batteries of the power supplyare being charged.

BRIEF DESCRIPTION OF THE DRAWING The above-mentioned and other featuresand objects of this invention and the manner of attaining them willbecome more apparent and the invention itself will be best understood byreference to the following description of an embodiment of the inventiontaken in conjunction with the accompanying drawing of an electricalschematic of the power supply of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing,there is illustrated a power supply 10 for use with a portable,hand-held cal- V culator circuit (not shown) such as, for example, theportable calculator circuit disclosed in US. Pat. application Ser. No.256,286, filed May 24, 1972, by James H. Buntingand assigned to the sameAssignee as the present invention which comprises a battery supplymodule 12 and a charging module 14.

Battery module 12 includes a positive terminal 16, a reference or groundterminal 18 and a negative terminal 20. A conventional off-on switch 22is connected electrically in series between positive terminal 16 and thearmature 24 of a single-pole, double-throw switch 26. The normallyclosed contact 28 of switch 26 is connected to the positive terminal 30of a plurality of series connected battery cells 32. In a specificembodiment, cells 32 comprise six nickel cadmium batteries which providea direct current potential of 7.2 volts. The negative terminal 34 ofseries connected cells 32 is connected to reference terminal 18.

A female plug indicated by dashed lines 36 includes three sockets 38,40, and 42. A diode 44 has its anode 46 connected to socket 38 and itscathode 48 connected to battery positive terminal 30. The normally opencontact of switch 26 is connected to socket 40, and reference terminal18 is connected to socket 42.

A filter capacitor 54 and a diode 56 are parallel connected betweenpositive terminal 16 and reference terminal 18 as shown.

A transistor chopper or oscillator circuit 60 includes input terminals62, 64 coupled to positive terminal 16 and reference terminal 18,respectively. Circuit 60 further includes a pair of transistors 70, 72,connected in push-pull configuration, emitters 74, 76 of transistors 70,72, being connected in common and the collectors 78, 80 thereof beingcoupled together via the end taps 82, 84 of the primary or input winding86 of a transformer 88.

Emitters 74, '76 are coupled to the center tap 90 of winding 86 via aseries connected resistor 92 and ca-' pacitor 94. Transformer 88 furtherincludes a feedback winding having end taps 102, 104 and a center tap106. Center tap 106 is connected at 95 to the commonly connectedterminals of resistor 92 and capacitor 94, and end taps 102, 104 areconnected to the bases 110, 112 of transistors 70, 72, respectively. Aphase shifting capacitor 114 is coupled between bases 110, 112 as shown.

Transformer 88 further includes an output winding 116 having end taps118,120 and a center tap 122, center tap 122 being coupled to ground orreference potential as at 124. A pair of diodes 130, 132 each have theircathodes connected to end taps 118, 120, respectively, and theiranodesconnected in common as at 134. Diodes 130, 132 are further connected tonegative terminal 20, diodes 130, 1 32 functioning as a full-waverectifier to rectify the signal received via output winding 116 frominput winding 86. A filter capacitor 136 is connected between the anodesof diodes 130, 132

. and ground.

The circuit 10 as described thus far provides a complete, portable powersupply for operating a small, portable, hand-held calculator circuit. Apositive polarity source is provided at positive terminal 16 directlyfrom batteries 32 and a negative polarity source is provided at negativeterminal 20 by means of the chopper" circuit 60.

To provide a means for charging the batteries 32 and to provide analternative source of power for operating the calculator circuit (notshown) when the same is being used at a location at which standard volt,60 cycle alternating current power is available, there is provided thecharging module 14. Module 14 includes a step-down transformer having aninput winding 152 which has connected thereto suitable plug means 154for connecting input winding 152 to a standard 120 volt AC power source.The output winding 156 of transformer 150 has oppositely disposed endtaps 158, 160. Connected across taps 158, 160 is a full-wave dioderectifier 162 which comprises four diodes 164, 166, 168, and connectedtogether in conventional manner. Rectifier circuit 162 includes outputterminals 172, 174 which are connected to a reference buss 176 and apositive buss 178, respectively.

Module 14 is provided with a male plug indicated by dashed lines 180,plug 180 being complementary to female plug 36. Plug 180 includes threepins 182, 184, and 186 which electrically connect to sockets 38, 40, and42, respectively,when the plugs 36 and 180 are engaged.

Plug 180 is further provided with an operating pin 188 (shown in dashediines) which operatively engages armature 24 of switch 26 when plugs 36and 180 are engaged. It will be observed that pin 188 moves armature 24from its normal position in which it electrically contacts contact 28and a second position in which armature 24 is in electrical contact withcontact 50.

Module 14 further includes a filter circuit 200 which includes a filtercapacitor 202, resistor 204, zener diode 206, and capacitor 208.Capacitor 202 is connected between positive buss 178 and reference buss176, resistor 204 and zener diode 206 are connected electrically inseries between positive buss 178 and reference buss 176, and capacitor208 is connected between the commonly connected terminal 210 of resistor204 and zener diode 206. A transistor 212 has its base 214 connected toterminal 210, its collector 216 connected to positive buss 178, and itsemitter 218 connected to pin 184. A load resistor 220 is connectedelectrically in series between positive buss 178 and pin 182.

It will now be seen that, when module 14 is engaged with module 12,switch 26 will be operated such that its armature 24 is in electricalcontact with contact 50. With means 154 connected to a 120 volt ACoutlet, the alternating voltage therefrom will be stepped down bytransformer 150, rectified by rectifier circuit 162, filtered by filtercircuit 200 with a positive, direct current potential being applied fromthe latter to pin 182. This potential in turn is applied via socket 38to the positive terminal of batteries 32' thereby charging the same.

Simultaneously, with module 14 energized, transistor 212 is renderedconductive. correspondingly, positive direct current potential isapplied to pin 184 via the collector 216 and emitter 218 thereof. Thispotential in turn is applied to the positive terminal 16 of module 12 bya socket 40, contact 50, armature 24, and off-on switch 22. g v

It will further be observed that zener diode 206 and transistor 212function as a regulator to regulate the potential of the voltageappearing at pin 184. Specifically, an increase in the voltage appearingon positive buss 178 will effect an increase in the potential applied tocollector 216 while the potential at base 214 is locked by zener diode206. This in turn increases the collector to base potential differenceand reduces the conductivity of transistor 212, increasing the potentialdrop thereacross, to thereby maintain the potential at pin 184relatively constant.

From the above description it can be seen that the power supply of thepresent invention provides a highly efficient means for generating bothpositive and negative polarity sources for the operation of portableelectronic equipment such as a portable, hand-held calculator circuit.The power supply circuit provides positive and negative sources havingsubstantially different power requirements and capabilities inaccordance with the requirements of the circuit being supplied. Becausethe source having the higher power requirements is provided directlyfrom the batteries without the use of additional circuit components,power losses are minimized. Similarly, the provision of a choppercircuit to provide a power source of opposite polarity and having alower power requirement which is operated from the batteries eliminatesthe need for additional battery cells, battery cells of different types,and, because the chopper circuit is utilized to generate the sourcehaving a lower power requirement, power consumption by the circuit isagain minimized.

Further, the novel power supply of the present invention provides asimple yet effective means for simultaneously operating a circuit froman alternating current power source when such is available and,simultaneously therewith, provides a means for charging the batteries inthe battery energized power supply circuit.

In a specific embodiment of the invention the follow- Transformer 150115 volts A. C. input volts A. C. output AA Nickel/Cadmium (6 units)+7.2 volts DC, 250 MA. max.

-7.2 volts D.C.,-20 MA.

Battery Cells 32 Output at terminal 16 Output at terminal 20 While therehave been described above the principles of this invention in connectionwith specific apparatus,- it is to be clearly understood that thisdescription is made only by way of example and not as a limitation tothe scope of the invention.

What is claimed is:

1. For use in a portable, hand-held calculator, a power supplycomprising positive, negative, and reference terminals, a plurality ofbatteries connected electrically in series between one of said positiveand negative terminals and said reference terminal for producing at saidone of said terminals a first direct current voltage of predeterminedpolarity, and means coupled to said batteries and between the other ofsaid positive and negative and said reference terminals for generatingat said other of said terminals a direct current voltage which is of apolarity opposite said predetermined polarity with respect to thevoltage occurring at said reference terminal, said generating meansincluding an oscillator circuit having an input circuit coupled to saidpositive terminal, an output circuit, a rectifier circuit, and meanscoupling said rectifier circuit to said output circuit, the currentcapacity of said generating means being substantially less than thecurrent capacity of said batteries.

2. The power supply of claim 1 wherein said coupling means includes atransformer having an input and an output winding, said input windinghaving end taps and a center tap, said oscillator including a pair oftransistors coupled in push-pull configuration to said end taps, saidcenter tap being connected to said one of said terminals, said rectifiermeans being coupled to said output winding.

3. The power supply of claim 2 wherein said output winding includes twoend taps and a center tap, said rectifier means including a full waverectifier having two input terminals and an output terminal, said inputterminal being connected to said last mentioned end tap, said outputterminal being connected to said other of said terminals, said centertap being connected to said reference terminal, said transformer furtherincluding a feedback winding having end taps and a center tap, saidtransistors having their bases connected to opposite ones of saidfeedback winding end taps, respectively, there being a first capacitorcoupled between said feedback winding end taps,-a second capacitorconnected between said common connected elements of said transistors andsaid feedback winding center tap and a resistor connected between saidfeedback winding and said input winding center taps.

4. For use in a portable, hand-held calculator, a power supplycomprising positive, negative, and reference terminals, a plurality ofbatteries connected electrically in series between said positiveterminal and said reference terminal, and means coupled to saidbatteries and between said negative and reference terminals forgenerating at said negative terminal a direct current voltage which isnegative with respect to the voltage occurring at said referenceterminal, said generating means including an oscillator circuit havingan input circuit coupled to said positive terminal, an output circuit, arectifier circuit, and means coupling said rectifier circuit to saidoutput circuit, a charging circuit disengageably coupled to said powersupply, said charging circuit including means for connecting saidcharging circuit to a source of alternating current, means coupled tosaid connecting means for generating a unidirectional, filtered currentsignal having a predetermined voltage level, means coupled to saidgenerating means includes a single-pole, single-throw switch hav-' ingfirst, second, and common contacts, said common contact being connectedto said positive terminal, said first contact being connected to saidbattery positive terminal, said second contact being disengageablyconnected to said output circuit, said battery connecting meansincluding a diode having its cathode connected to said battery positiveterminal and a resistor connected in series between said signalgenerating means and the anode of said diode.

6. The power supply of claim 5 wherein said regulating means includes aresistor and a zener diode connected electrically in series between saidsignal generating means and said reference terminal, a transistor havingits collector'and emitter connected electrically in series between saidgenerating means and said mod- .ule positive terminal and its baseconnected to the cathode of said zener diode, and a capacitor connectedbetween said base and said reference terminal.

7. The power supply of claim 5 wherein said coupling means furtherincludes a multi-pin plug having selectively engageable male and femaleportions, said common contact being normally connected to said firstcontact, said plug including means for connecting said common contact tosaid second contact and disconnecting said common contact from saidfirst contact when said male and female portions are engaged.

1.! i I i

1. For use in a portable, hand-held calculator, a power supplycomprising positive, negative, and reference terminals, a plurality ofbatteries connected electrically in series between one of said positiveand negative terminals and said reference terminal for producing at saidone of said terminals a first direct current voltage of predeterminedpolarity, and means coupled to said batteries and between the other ofsaid positive and negative and said reference terminals for generatingat said other of said terminals a direct current voltage which is of apolarity opposite said predetermined polarity with respect to thevoltage occurring at said reference terminal, said generating meansincluding an oscillator circuit having an input circuit coupled to saidpositive terminal, an output circuit, a rectifier circuit, and meanscoupling said rectifier circuit to said output circuit, the currentcapacity of said generating means being substantially less than thecurrent capacity of said batteries.
 2. The power supply of claim 1wherein said coupling means includes a transformer having an input andan output winding, said input winding having end taps and a center tap,said oscillator including a pair of transistors coupled in push-pullconfiguration to said end taps, said center tap being connected to saidone of said terminals, said rectifier means being coupled to said outputwinding.
 3. The power supply of claim 2 wherein said output windingincludes two end taps and a center tap, said rectifier means including afull wave rectifier having two input terminals and an output terminal,said input terminal being connected to said last mentioned end tap, saidoutput terminal being connected to said other of said terminals, saidcenter tap being connected to said reference terminal, said transformerfurther including a feedback winding having end taps and a center tap,said transistors having their bases connected to opposite ones of saidfeedback winding end taps, respectively, there being a first capacitorcoupled between said feedback winding end taps, a second capacitorconnected between said common connected elements of said transistors andsaid feedback winding center tap and a resistor connected between saidfeedback winding and said input winding center taps.
 4. For use in aportable, hand-held calculator, a power supply comprising positive,negative, and reference terminals, a plurality of batteries connectedelectrically in series between said positive terminal and said referenceterminal, and means coupled to said batteries and between said negativeand reference terminals for generating at said negative terminal adirect current voltage which is negative with respect to the voltageoccurring at said reference terminal, said generating means including anoscillator circuit having an input circuit coupled to said positiveterminal, an output circuit, a rectifier circuit, and means couplingsaid rectifier circuit to said output circuit, a charging circuitdisengageably coupled to said power supply, said charging circuitincluding means for connecting said charging circuit to a source ofalternating current, means coupled to said connecting means forgenerating a unidirectional, filtered current signal having apredetermined voltage level, means coupled to said generating means forregulating said voltage level, said regulating means including an outputcircuit, and means for simultaneously and selectively coupling saidoutput cirCuit to said positive terminal and coupling said batterypositive terminal to said generating means and disconnecting saidbattery positive terminal from said positive terminal when said moduleis coupled to said power supply and for connecting said battery terminalto said positive terminal when said module is disconnected from saidpower supply.
 5. The power supply of claim 4 wherein said coupling meansincludes a single-pole, single-throw switch having first, second, andcommon contacts, said common contact being connected to said positiveterminal, said first contact being connected to said battery positiveterminal, said second contact being disengageably connected to saidoutput circuit, said battery connecting means including a diode havingits cathode connected to said battery positive terminal and a resistorconnected in series between said signal generating means and the anodeof said diode.
 6. The power supply of claim 5 wherein said regulatingmeans includes a resistor and a zener diode connected electrically inseries between said signal generating means and said reference terminal,a transistor having its collector and emitter connected electrically inseries between said generating means and said module positive terminaland its base connected to the cathode of said zener diode, and acapacitor connected between said base and said reference terminal. 7.The power supply of claim 5 wherein said coupling means further includesa multi-pin plug having selectively engageable male and female portions,said common contact being normally connected to said first contact, saidplug including means for connecting said common contact to said secondcontact and disconnecting said common contact from said first contactwhen said male and female portions are engaged.